While most of the nation has this week been focussed on which horse crosses the finishing line first, scientists announced that they have completed mapping the horse genome.

The findings, reported in today's edition of Science, not only provides insights into the genetic make-up of the horse, but could become a valuable tool in detecting diseases in other species.

Geneticist and lead author Professor Claire Wade of the University of Sydney and her colleagues sequenced the horse genome using a technique called capillary sequencing, which was the same technique used to sequence the human genome.

She says the horse genome consists of 2.7 billion letters, which is slightly smaller than that of the human, but larger than the mouse and dog genomes.

By studying the horse genome, Wade says, scientists can use it to better understand human genetic disorders.

She says, as animals evolve it's expected that those parts of the DNA that do something important stay unchanged.

"If we can see the same thing in a horse sequence that we can see in a human sequence that gives us a clue that that part of the DNA is important."

Wade says as with all mammals, there are a lot of genetic similarities between humans and horses.

"The chromosomes have not been rearranged very much between the mammalian common ancestor and humans."

Human companions

Throughout history, horses have been close human companions since they were domesticated between 4000 and 6000 years ago.

But Wade says it's very difficult to determine a true genetic signature of domestication.

Almost all horse breeds are now domesticated so there is nothing to compare them to, she says.

Even the Przewalski horse, a wild breed found in Mongolia, which was thought to be an ancestor of domestic horses, was found to be almost genetically identical to other breeds of domestic horse, she says.

But by far the most exciting discovery in the genome project was the identification of a new centromere, called a neocentromere, on chromosome 11, says Wade.

"Centromere's are typically nucleotide sequences that stabilise the DNA during cell division."

Wade says the neocentromere, which is fixed throughout the species, is a sign of where in evolutionary history horses diverged from other species of their family, such as donkeys and zebras.

She says they will be able to use the information within the neocentromere to understand how centromeres work in other species.

Genetic maps

As well as sequencing the genome, the team were also able to develop a map of genetic markers, known as SNP's, which are used to compare DNA sequences between individual horses.

"It helps us to map the genes that affect horse health," says Wade.

The genetic markers were mapped from seven horses that were geographically dispersed to ensure different aspects of horse ancestory were represented, she says.

"That ensures the resource is useful for all horse breeds."

Dr Natasha Ellis, also of the University of Sydney, is currently using the genome research to study a specific gene called ACE, which is associated with blood pressure and may be linked to racing performance.

"Having the horse genome is very helpful to look at individual genes. It also helps researchers and breeders," she says.